Haiti's southern city of Jeremie suffered "complete destruction" when it was hammered by Hurricane Matthew, the CARE relief agency said on Thursday.

"It's complete destruction in Jeremie," CARE Haiti country director Jean-Michel Vigreux tweeted. "About 80 percent of the buildings are gone. All phone lines and electricity are gone. Access is completely cut off, and everyone is running out of food and money."

Further south in Les Cayes -- home to a major Haitian port -- an AFP reporter found the cathedral's roof completely blown off.

The city center managed to resist significant damage thanks to its concrete construction, but Matthew's pounding rains and violent wind gusts devastated the Croix-Marche a Terre neighborhood close to the shore. Coconut trees smashed into dozens of houses, destroying many of their flimsy sheet-metal roofs.

The storm also ravaged banana and mango crops in the surrounding fields.

At least 108 people were killed in vulnerable Haiti -- the poorest country in the Americas -- during Matthew's assault, which caused severe damage in several more countries as it blasted through the Caribbean.

The ferocious Category Four hurricane is expected to hit Florida late Thursday. US President Barack Obama declared a federal state of emergency as residents fled inland.